This invention relates to the field of orthopedic surgery and particularly to the instrumentation and methods for minimally invasive total hip replacement.
A conventional total hip replacement is performed through a 10-14 inch incision located either anterior, lateral or posterio-lateral overlying the hip joint. The hip is dislocated either anteriorly or posteriorly.
This large incision is necessary to allow preparation of the acetabulum and proximal femur using instruments held at various angles to the acetabulum and proximal femur. The soft tissue dissection through skin, subcutaneous tissue, deep fascia, and muscles is associated with significant pain and time for healing.
The head and part of the neck of the femur is visualized and removed using a saw. The acetabulum is prepared by reaming to the desired size and using various sized trials until the optimum size is determined. The desired acetabular prosthesis is impacted in optimum position in the acetabulum and one of various sized liners is impacted into the posthesis. The prosthesis is fixed to bone either by cement or by porous coating that allows fixation by bony ingrowth into the prosthesis.
The proximal femur is then prepared by reaming and adjustment of neck length and varying sized trials are used to determine the optimum size. Trial neck lengths are used to determine the proper fit and leg length and the femoral stem is fixed top bone either by cement or porous coating on the prosthesis. The proper prosthetic head and neck length is then attached and the final fit, stability, and leg length are confirmed.
What is needed in the art is instrumentation along with procedures which reduce the soft tissue trauma and facilitate placement of the acetabular prosthesis.
U.S. Pat. No. 6,010,535 issued Jan. 4, 2000 to Shah discloses a surgical technique performed through arthroscopic and fluoroscopic guide procedures in which the natural ball of the Femur and the natural Acetabulum are left, largely, intact. A small hole is drilled through the Trochanter and ball of the Femur. The hole is extended, in the same plane, into the Acetabulum. A guide wire is inserted through the hole in the Femur and anchored in the Acetabulum. A reamer follows the guide wire enlarging the hole in the Femur to about an inch. Another reamer is inserted along the guide wire to ream a small spherical cavity in the natural Acetabulum. A small cup member is then secured in this cavity in the Acetabulum. A small ball may then attached to the exterior of the natural ball to be seated in the small cup member in the Acetabulum. The small ball and cup member, respectively, are secured by bone screws. This approach avoids the large conventional incisions with accompanying hospital stay and rehabilitation period. This procedure is obviously limited to those situations in which the ball-and-socket of the natural hip joint are still functional and pain free.
Sharratt, U.S. Pat. No. 6,315,718, issued Nov. 13, 2001, discloses the conventional surgical procedure for total hip replacement. Sharratt is concerned with the physical strength required on the part of the surgical team to retract and hold the Femur distant from the Acetabulum during surgery. To that end the patent is related to a surgical table mounted retractor apparatus capable of fixing the leg during surgery.
Accordingly, it is an objective of the instant invention to teach a minimally invasive technique for total hip replacement using a small incision to create a surgical field to visualize the acetabulum.
It is a further objective of the instant invention to teach the use of instrumentation to facilitate anatomically correct placement of an artificial acetabulum.
Another object of the invention is to teach the insertion of a properly oriented guide wire from the exterior of the patient""s body into the surgical field.
It is yet another objective of the instant invention to teach the use of instrumentation with removable working heads for changing components within the surgical field.
The minimally invasive technique of this invention includes making a small, 2xc2xd to 3 inches, incision to create a surgical field to view the head of the femur and the acetabulum during the preparation of each for implantation of the prosthesis. One end of a guide is inserted into the acetabulum through the surgical field and manipulated to the correct angle for reaming the acetabulum. This results in placing the other end of the guide at the proper point exteriorly of the patient""s body to access the surgical field at the correct angle.
A guide wire is inserted through the other end of the guide and through the patient""s body, at the correct angle, to engage the first end of the guide in the surgical field. In some cases, a second small incision, approximately 1 inch, is used for positioning the other end of the guide and inserting the guide wire. A common shaft may be inserted along the guide wire to operatively connect the surgical field and the exterior of the body, without an incision. As the stages of the hip replacement progress, the surgeon may replace different working heads on the end of the shaft which is in the surgical field without the necessity of removing the shaft from the body.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.